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Technology: Spinning screen TV gives ‘real 3-D’ images

VISITORS to a trade exhibition in Dallas, Texas, this week will see
the first working demonstration of a TV display system which gives three-dimensional
images when viewed from any angle, by any number of people, without the
need to wear coloured spectacles.

The developers, the American electronics company Texas Instruments,
claim that the new 3-D system, called OmniView, is the first to create an
image with real depth, rather than one which is flat but is made to appear
deep by optical trickery. With the new system, the perspective changes with
the viewing angle, just as it does with a real solid object.

The company has built a prototype, demonstrated at the Siggraph ’90
exhibition, to prove that the system works, and is now looking for developers
to manufacture OmniView under licence.

The heart of OmniView is a large double helical disc made of translucent
material. This disc rotates on the end of a drive shaft and viewers look
at it from an angle. As the double helix rotates it presents a screen area
which continually varies in depth – like the threads of a large moving screw.

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A laser beam scans the disc as it turns, much like the electron beam
inside a TV tube which scans the screen surface. Also like the electron
beam in a TV tube, the brightness of the laser beam varies as it scans the
disc to create an image. The beam creates a raster pattern of light on the
disc surface, which the viewers’ eyes fuse into an image.

This image has depth because the distance between the viewer and the
display area created by the disc changes as the disc rotates. The trick
is to synchronise the scanning of the laser and rotational speed of the
disc with the image signal.

In the first prototype, the disc rotates 10 times a second and the laser
beam can be modulated in brightness 10 000 times a second. This allows the
system to produce a picture resolution of 750 X 750 picture points or pixels,
the company claims, which is better than conventional TV.

If three lasers are used, one each for red, green and blue image content,
the result is a full-colour picture. Resolution can be improved by using
more lasers, each scanning different parts of a large disc.

Although OmniView could be used for cinema presentation, Texas Instruments
is more interested in commercial applications. Air traffic controllers could
view a large volume of air space in 3-D, with several controllers sharing
the same large display instead of each watching their own radar screens.
Colour coding would identify aircraft, buildings and protected air space.

The same technique is appropriate for weather displays and war room
displays of military movements. Texas Instruments also suggests molecular
modelling, medical imaging and remote control of robots as future applications.